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Equiaxial nano-crystals Nb3Al superconductor prepared by optimized mechanically alloying

Zhang, Wenjie, Li, Pingyuan, Zou, Xiaofeng, Yu, Zhou, Yang, Xinsheng, Pan, Xifeng, Zhao, Yong, Zhang, Yong
Journal of materials science 2019 v.54 no.6 pp. 5022-5031
chemical composition, magnetic fields, microstructure, milling, nanocrystals, superconductivity, temperature
The influence of the original nominal chemical composition, milling time, sintering temperature and holding time was studied systematically on the phase formation, microstructure and superconductivity of mechanically alloyed Nb₃Al. By optimizing the process, we have successfully prepared high-performance Nb₃Al superconductor. Samples with original nominal composition of Nb-27 at.%Al were milled for 3 h and sintered at 900 °C for 1 h, resulting in an entire A15 superconducting phase, except a few negligible Nb₂Al phase. The superconducting critical transition temperature (Tc) and the upper critical field at absolute zero (Hc₂(0)) reached 15.7 K and 28.1 T, respectively. It should be noted that the superconducting critical current density (Jc) was still as high as 6.3 × 10⁴ A cm⁻² at a temperature of 4.2 K under an applied magnetic field of 7 T, as well as a maximum flux pinning force (Fₚ,ₘₐₓ) of 6.23 × 10⁹ N m⁻³ in the whole magnetic field range at 4.2 K. All of the results could be attributed to the microstructure of the sample with equiaxial nano-crystals.